In industrial duplication of magnetic tape, the sounds to be duplicated are initially recorded on professional magnetic tape, suited to systems that are proper for all forms of processing, (e.g. assembly, equalization, etc.). Eventually these tapes are recorded on stereophonic tracks. Typically each tape is loaded with just one program comprised of a number of single musical pieces, a single musical piece of suitable length or a selection of limited pieces.
The magnetic tapes to be produced on an industrial scale must have characteristics which make them suitable for use on commercial tape playback devices. The recording speed of these tapes is a fraction of the recording speed of the tapes prepared in recording studios. In this way, the quantity of tape necessary to record a program is reduced in size, while the quality of the produced sound is generally satisfactory for the normal commercial market.
In the manufacturing process, a copy is made from the professional tape onto an intermediate tape. The intermediate tape is recorded at a speed that is intermediate between the speed of the professional tape and the speed of the final products (e.g. audio or music cassettes). The intermediate tape has a plurality of recorded tracks, at least one for each stereophonic program, and includes all the processing necessary to achieve the final desired sound. This tape is usually called a "master" tape.
The master tape, which is recorded in analog form, is then reproduced (played back) at a speed that is much higher than the speed at which the tape was recorded (generally 64 times higher, but sometimes much more). If the speed is, for example, 64 times greater than the speed at which the final product will be played back to a listener, a an hour of sound is copied in about 28 seconds. Under this method, the frequencies of the sound are automatically multiplied by the same speed factor.
The master tape is usually in the form of a loop. This permits it to be read continuously. Each full turn of the tape represents one entire program which, when it is played back on a "loop bin," is simultaneously recorded on a recorder generally called a "slave." Typically, a plurality of these slaves are connected to the outputs of the loop bin to obtain multiple copies of the same program, simultaneously. Thus, the number of copies of the same program corresponds, for each passage of the master tape, to the number of the slaves connected to the outputs of the loop bin.
In summary, sounds are initially recorded on professional tapes in a manner that permits them to receive all the necessary processing to make them duplicatable. Then the sounds are transferred, according to current standards, onto an intermediate or master tape. At this point, industrial production is begun.
One drawback of the above-described prior art is that such duplicating systems have several moving parts which are subject to wear. The primary part which is subject to this wear is the master tape. This tape wears out because it is subjected to a large number of high speed passages over a reading head during the duplication process. Over time, the tapes undergo changes which gradually erode the level of quality of the original recorded sound.
In actual production, programs of medium length are typically alternated with very short programs. In fact, from an examination of the programs which are generally duplicated, it has been noted that the majority of the programs have lengths which are shorter than half of the maximum allowed length. Only a very small fraction of programs actually approach the maximum allowed length. This means that the capacity of the tape, on which the programs to be duplicated are recorded, is not entirely used.
The current trend in the digitization of recorded sound has encouraged the manufacturers of recorded sounds to spread the use of digital systems to all the stages of sound duplication, including the recording of the final product, such as analog audio cassettes. One problem with digitally recorded sounds is that there is no easy way to copy such a recording at speeds higher than the speed at which the sounds were originally recorded. This is because of the presence of movable mechanical members in players/recorders.
While the duplication carried out by the prior art allows the programs to be duplicated at higher speeds than the original recorded speed, two basic limits still exist which have not been overcome. These limits essentially are the poor utilization of the full length of usable master tape on which the programs are recorded, and the qualitative degeneration to which the moving master tape is subjected during its high speed playback of the program to be duplicated.
Therefore, the prior art allows the reproduction of the information of the analog master tape, the corresponding recording on magnetic media, the analog-to-digital conversion and vice-versa and the recording, in an analog form, on the final support. A microprocessor runs all the foregoing phases, including controlling the synchronization of the recording of the data on the magnetic media and the analog-to-digital and digital-to-analog conversion.